人工湿地污水处理技术因污染物去除能力强、投资少、维护成本低以及具有美学价值等优点而受到广泛关注。但如何更有效的利用人工湿地、多级人工湿地中如何排列植物顺序、不同浓度污水对湿地的影响以及污染物的迁移转化规律都仍然是需要深入研究的重点。本文以人工配制的不同浓度的生活污水以及城市生活污水为处理对象，构建多介质人工湿地系统，并建立纯土壤湿地和纯基质湿地作为空白对照，研究土壤、基质以及植物在净化过程中的作用，并探究多介质人工湿地系统对各污染物的主要去除过程及其净化机制、人工湿地系统中DO及pH值对去污效率的影响，主要研究结果如下：（1）土壤系统在处理低浓度污水时和基质系统具有相似的净化性能，但在应对高浓度污水时土壤系统的净化效率下降的十分显著，基质系统具有更稳定的去除效果。（2）基质对TN、NH4+-N、TP有十分明显的吸收作用，在去除氮污染物时，植物起到很好的辅助净化作用，而在净化TP的过程中，基质的作用占主导地位，植物的辅助吸收作用有限。基质对NO3--N去除的作用不强，其净化途径主要依靠反硝化作用以及植物的吸收作用。（3）各湿地单元对不同浓度污水的净化效率各有变化，其净化能力的排序也各不相同，但是应遵循的原则是，对高浓度污水去除效果好的湿地单元应置于多级湿地的前端，对低浓度污水去除效果好的单元应置于后端，填充有基质的单元应置于前端，出水清澈、溶解氧富足的单元应置于湿地末端。（4）DO与NH4+-N、NO3--N、TP净化率存在显著的负相关关系，与TN净化率达到极显著水平（r=-0.692，P <0.01），pH与DO存在极显著的正相关关系（r=0.601，P<0.01）。（5）污染物的降解主要发生在前几级湿地，随着污水运行至后续湿地单元污染物降解速率逐渐变小。（6）污水处理过程中，沿程pH先降低再升高的拐点可作为氨氮氧化作用结束的标志，pH升高再降低的拐点可作为反硝化作用结束的标志。（7）污水在多介质人工湿地系统中运行过程中DO含量会先降低再升高，这是由于在系统的始端主要发生有机质的降解、氨氮的氧化等反应，会消耗DO，导致DO降低，而当有机质降解完全，硝化反应结束时，植物的光合作用、根际输氧作用以及大气复氧作用又会使系统DO升高。; Constructed wetlands for wastewater treatmentattract people’s attention for its advantages such as high removal efficiency, low investment, low maintenance and ecological functions. But how to use constructed wetland more effectively, how to make arrangements for plants in multi-stage constructed wetlands, the influence of different concentration of wastewater on wetland, and the pullutants migration and transformation law are still need to be further research. In this paper, the multi-medium constructed wetlands system was built to treat the different concentrations of artificial sewage and the actual sewage from a residential area of Yantai. At the same time, a soil system and a substrate system were built as the blank control. The main contents of this study include: the functions of soil, substrates and plants in the purification process, the transfer and degradation laws of the pollutants in the systems, effect of DO and pH on treatment efficiencies in the multi-medium constructed wetlands. The main results were summarized as following:(1) The soil system and substrate system had the similar purification capacity when treating low concentration sewage. But when dealing with high concentration sewage, purification efficiency of soil system declined very significantly, and the substrate system had a more stable removal efficiency.(2) Substrates had obvious absorption effect on TN、NH4+-N and TP and plants had very good auxiliary effect when treating nitrogenous pollutants. However, the functions of substrates were dominant in the process of treating TP and the functions of plants were limited. In addition, substrates had not a strong absorption effect on NO3--N, and the main removal way were denitrification and the absorption of plants.(3) Every wetland units had different removal efficiency when treating different concentration sewage. But some principles should be followed: the unit had high removal efficiency on high concentration sewage should be arranged to the front of the system, while the unit had high removal efficiency on low concentration sewage should be arranged to the back of the system. And the unit that had substrates should be arranged to the front of the system, the unit whose outflowwas bright and clear should be arranged to the end of the system.(4) There were significant negative correlation between DO and the removal efficiency of NH4+-N, NO3--N, TP. There was greatly significant negative correlation between DO and the removal efficiency of TN (r=-0.692，p<0.01) . There was greatly significant positive correlation between pH and DO (r=0.601，p<0.01) .(5) The degradation of pollutants mainly happened in the first few stages of the system. As sewage running to subsequent wetland unit pollutant degradation rate decreased gradually. (6) In the process, the break-point of the pH curve with reduction and rising was suggested to be an indicator of the end of the NH4+-N reaction. The break-point of the pH curve with rising and reduction was suggested to be an indicator of the end of denitrification. (7) In the process of treating the sewage, variation of DO along the flow path was decreased at first, then increased. The reason was that the degradation of organic matter and nitration reaction would consume DO in the first stages of system. Then, photosynthesis of plants, root oxygen role and atmospheric reaeration would make DO to rise.
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